1. Field of the Invention
The present invention relates to optical molding apparatuses, optical molding methods, and optically molded products. In particular, the present invention relates to an optical molding apparatus and an optical molding method that can shorten the time necessary for molding a high-precision molded product, and to an optically molded product that can be molded in a shorter time.
2. Description of the Related Art
In related art, when a three-dimensional model (molded product) is to be formed using three-dimensional-shape data created by computer aided design (CAD), a numerically-controlled machining device, for example, is used, which means that the three-dimensional model is formed by machining.
In recent years, a method called rapid prototyping (RP) used for forming a three-dimensional model without machining has been attracting attention at many production sites. In rapid prototyping, a manufacturing technique called a lamination-molding technique is employed. In this technique, a three-dimensional model is formed by creating thin sheets defining cross-sectional shapes of the three-dimensional model, which are thin slices of the three-dimensional model, on the basis of three-dimensional-shape data of the three-dimensional model, and then stacking the thin sheets defining the cross-sectional shapes one on top of the other.
Rapid prototyping can be classified into the following methods depending on how the thin sheets defining the cross-sectional shapes are created: an optical molding method that employs ultraviolet curable resin, a fused deposition modeling (FDM) method in which layers of thermoplastic resin are laminated by extrusion, a selective laser sintering (SLS) method in which layers are laminated by melting and adhering a powder material, a laminated object manufacturing (LOM) method in which thin sheets of paper are laminated, and an ink-jet method in which powder or curing catalyst is emitted to form a laminate.
For example, in the optical molding method, three-dimensional-shape data of a three-dimensional model created by CAD is converted to stereo lithography (STL) which is a format that expresses the surface of the three-dimensional model with small triangular surfaces. The STL is then received by an optical molding apparatus.
From the three-dimensional-shape data, the optical molding apparatus creates cross-sectional-shape data items, which are obtained by slicing the three-dimensional model at a fixed interval of, for example, about 0.1 mm to 0.2 mm. Based on each cross-sectional-shape data item, the optical molding apparatus determines an exposure range to which light is to be emitted on the surface of photo-curable resin in the liquid state. For each layer corresponding to one cross-sectional-shape data item, the optical molding apparatus emits light according to the cross-sectional-shape data item to the exposure range on the surface of the liquid photo-curable resin, and shifts a shiftable stage disposed in the liquid photo-curable resin downward in an orthogonal direction in accordance with the thickness of each slice of the three-dimensional model. Then, the optical molding apparatus repeats the light emission process and the shifting process of the shiftable stage from the cross-sectional-shape data item for the lowermost layer to the cross-sectional-shape data item for the uppermost layer, thereby forming the three-dimensional model.
Methods for emitting light to the surface of the photo-curable resin in the optical molding apparatus include a beam-scanning method performed by scanning a light beam, a spatial-light-modulator (SLM) projecting method performed by emitting light collectively using a spatial light modulator, such as a liquid crystal panel, and a method with the combination of the beam-scanning method and the SLM projecting method.
In the method with the combination of the beam-scanning method and the SLM projecting method, light is emitted collectively to the exposure range on the surface of the photo-curable resin by using the spatial light modulator, and a light beam is scanned along the contour of each cross-sectional-shape data item, whereby a three-dimensional model with a clear contour can be molded.
Japanese Unexamined Patent Application Publication No. 5-77323 discloses an optical molding apparatus that can adjust the distance between the surface of the photo-curable resin and a mirror, which is used for scanning a light beam, in accordance with the size of the three-dimensional model.